One of the most common accessories for a mobile telephone is a hands-free kit which enables hands-free use of the mobile telephone while a vehicle is being driven. Generally speaking, a hands-free kit includes a speaker, microphone and amplifier which are external to the mobile telephone. The hands-free kit might also include a physical entrapment, such as a cradle, to receive and hold a mobile telephone while the car is being driven. The cradle provides an electrical connection to the mobile phone when the phone is nested in the cradle. The external speaker and microphone are connected directly or indirectly to the cradle. When the driver leaves the vehicle, the mobile telephone can be removed from the cradle and carried.
One problem with prior art designs for hands-free kits is that they require a separate speaker and power amplifier. These components are already part of a car stereo system which is present in the vast majority of vehicles manufactured today. Thus, the current designs duplicate components which are already present.
Another drawback with prior art designs is that there is no easy way to control the volume of the speakers. In current designs, volume control circuitry is included in the mobile telephone. Access to the volume control functions is provided by the touch pad and display on the mobile phone. The user can change the volume by pushing buttons and scrolling through menus on the display. This method of volume control requires a great deal of attention (which defeats the purpose of a hands-free kit). Further, there is no easy way to adjust the volume during a call.